A gas sensor module of this type includes, for example, a premolded package having an injection-molded lead frame that includes multiple leads forming bond pads on the inside of the premolded package and connecting pins on the outside for contacting with a substrate, for example a p.c. board. The gas sensor, which is formed, for example in the form of a chip stack, by a sensor chip having a diaphragm and an infrared-sensitive measuring structure, and a cap chip covering the measuring structure, is generally glued to the bottom of the package and contacted with the lead contact pads via wire bonds. The package interior can be filled with a passivation gel to protect the wire bonds. One or more optical filter chips, which are selectively transparent to IR radiation within certain spectral ranges and thus allow the IR radiation to be measured within a spectral range that is relevant for a specific gas and, for example, a reference spectral range, are attached to the cap chip or the bottom of the cover.
The connecting pins are bent downward so that the bottom of the gas sensor module can be attached to the substrate. An IR lamp, for example an incandescent light bulb which operates in the low-current range, is provided at a lateral distance therefrom, an absorption distance or an absorption chamber being definable between the IR lamp and the gas sensor module, for example by a reflector that is attached to the top of the substrate and reflects the IR radiation emitted by the IR lamp to the gas sensor module. The absorption of the gas or gas mixture in the absorption chamber can thus be used to detect the gas concentration.
Using a standard assembly method, the gas sensor module is mounted on the substrate, on which not only a variety of other structural components, but also the IR radiation source is located at a defined distance from the detector. The reflector is mounted above the lamp and the gas sensor to concentrate the IR radiation. The dimensioning of the sensor package module in the lateral direction and in height substantially determines the minimum reflector size, since the reflector surrounds the gas sensor module.